Not applicable.
Not applicable.
This invention relates to a coupler for removably locking a hub to a shaft.
Couplers for removably locking a hub axially on a shaft are well known, see e.g., U.S. Pat. Nos. 4,900,181; 4,960,344; and 5,632,568. The hubs can have an end which is the yoke of a universal joint for attachment to a power drive assembly rotating the shaft. For example, such couplers are often used to couple the power input shaft of an agricultural implement to the power takeoff shaft of a tractor. Typically, the hub is internally splined to match the external splines on the tractor""s power takeoff shaft, so as to establish rotary transmissive coupling between the hub and the power takeoff shaft.
The hub is typically locked onto the shaft by locking members that can slide in radially extending slots through the hub so as to engage a circumferential groove or raceway in the splined power takeoff shaft of the tractor. A collar around the outside of the hub is biased into a locked position by a spring so as to prevent the locking members from backing away from the shaft.
The coupler disclosed in U.S. Pat. No. 4,900,181 has a stop formed in the collar that extends radially inwardly to abut a stop in the hub when the collar is tilted or cocked with respect to the axis of the shaft. When the shaft is inserted into the hub, locking members in the hub are moved radially outward to center the collar and disengage the stops. The collar can then be moved to lock the hub onto the shaft under the bias of a spring. However, the collar can be locked in a disengaged position even though the shaft is fully inserted into the hub. Thus, the hub may appear properly locked onto the shaft despite the collar being disengaged.
U.S. Pat. No. 5,632,568 provides a coupler in which the locking collar cannot be disengaged with the shaft fully inserted into the hub. In particular, the hub has a stop that a locking collar engages when cocked in a disengaged position. Inserting the shaft into the hub drives uncocking members radially outward to position the locking collar concentric with the hub so as to disengage it from the stop. The locking collar can then be slid to cam the locking members inwardly to lock the hub onto the shaft under the bias of the spring. The uncocking members prevent the collar from being cocked so that the collar cannot engage the stop and be locked in the disengaged position.
While this provides a significant improvement, like the former coupler, this coupler has a tilted or cocked collar. The collar thus gives the appearance of being loose or damaged. More importantly, this can be disadvantageous because if the collar is bumped inadvertently, it can spring into the locked position before the shaft is inserted into the hub. Also, with the collar in the locked position, the shaft cannot be inserted into the hub, thereby frustrating the user. Thus, the user must recognize this and manually reset the collar before coupling the shaft to the hub.
U.S. Pat. No. 4,960,344 discloses a coupler in which an eccentrically biased control ring and a concentric locking ring inside the collar operates locking members so that the collar remains concentric with the hub throughout its range of movement. When the shaft is inserted into the hub the locking members drive the control ring outward concentric with the axis to disengage from a stop surface and allow the collar to slide and lock the hub onto the shaft. In this position, the locking ring retains the locking members in engagement with the shaft. However, like the first described coupler, the locking collar can be moved and locked in the disengaged position even though the shaft is seated in the hub.
Accordingly, there is a need in the art for an improved coupler assembly.
The present invention provides a coupler assembly for axially locking a hub to a shaft. The hub has an axial bore and radial slots spaced apart axially. A collar fits concentrically about the hub and can be slid thereon from a released position to a locked position. A collar latch assembly includes a latch ring and a release member radially movable in a radial slot. When the collar is in the released position, the latch ring is eccentric about the hub and the release member and engages a radial surface of the hub on one side of the latch ring and a radial surface of the collar on the other side of the latch ring to prevent movement of the collar. When the collar is in the locked position and the shaft is inserted in the bore of the hub, the latch ring is centered about the hub in a channel of the collar to allow the collar to slide along the hub so that a locking member can move in a radial slot to engage a recess in the shaft. The release member is in a radially outward location so as to prevent engagement of the latch ring with the hub while the shaft is in the hub.
In a preferred form, the hub has a first set of two radial slots angularly spaced about 180 degrees from each other and containing ball-shaped locking members. The hub also has a second set of four radial slots containing ball-shaped release members and angularly spaced about 90 degrees from each other and axially spaced from the two locking member slots.
In another form, the collar latch assembly further includes a spring, preferably a leaf spring, biasing the latch ring eccentrically with respect to the hub. The collar latch assembly further includes a compression spring disposed about the hub and biasing the collar toward the locked position. The compression spring is captured between the collar and a stop ring which may be integral with or otherwise fixed with respect to the hub.
One object of the invention is to provide a coupler that cannot be locked in a released position when the shaft is engaged in the hub. This is accomplished by a set of release members that prevent the latch ring from engaging the hub, and thereby latching the collar, when the shaft is in the hub. This latching lockout occurs automatically when the shaft is inserted in the hub.
Another object of the invention is to provide a coupler with a locking collar that is maintained concentrically with the hub throughout its range of movement. This is accomplished by providing a latching mechanism for retaining the collar to the hub.
Another object of the invention is to provide a coupler that automatically locks the shaft to the hub upon insertion of the shaft into the bore of the hub. Inserting the shaft into the hub moves the release members radially outward to disengage the latch ring, thereby allowing the collar to slide to the locked position, under the force of the compression spring, in which the locking members are held in engagement with the recess of the shaft.
The foregoing and other objects and advantages of the present invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof and in which there is shown by way of illustration a preferred embodiment of the invention. Such an embodiment does not necessarily represent the full scope of the invention, however, and reference must be made therefore to the claims for interpreting the scope of the invention.